Ships' routeing measures have been introduced in a number of coastal waters to:
reduce the risk of collision between ships in areas of high traffic densities;
keep shipping away from environmentally sensitive sea areas;
reduce the risk of grounding in shallow waters.
The use of ships routeing measures should form part of the passage plan.
Ships' routeing measures can be adopted internationally by IMO. Such schemes are recommended for use by, and may be made mandatory for, all ships, certain categories of ships or ships carrying certain cargoes. Mandatory ships routeing schemes should always be used unless the ship has safety reasons for not following them.
IMO routeing schemes will be shown on charts with a note of any pertinent information as to their use. Details may be described in Sailing Directions. The IMO publications Ships Routeing and Amendments to Ships Routeing contain full descriptions of each scheme and any rules applying, but this publication is produced mostly for the benefit of administrations. It is not kept up to date as regularly as nautical publications, which should always
be looked at for the latest information.
Elements used in routeing systems include:
traffic separation scheme - a routeing measure aimed at the separation of opposing streams of traffic by establishing traffic lanes.
traffic lane - areas within defined limits in which one-way traffic flows are established.
separation zone or line - a means to separate traffic lanes in which ships are proceeding in opposite or nearly opposite directions in order to separate traffic lanes from adjacent sea areas or to separate different traffic lanes.
roundabout - a separation point or circular zone and a circular traffic lane within defined limits;
inshore traffic zone - a designated sea area between the landward boundary of a traffic separation scheme and an adjacent coast.
recommended route - a route of undefined width, for the convenience of ships in transit, which is often marked by centreline buoys.
deep water route - a route which has been accurately surveyed for clearance of sea bottom and submerged articles.
archipelagic sea lane - sea lanes designated for the continuous and expeditious passage of ships through archipelagic waters.
precautionary area - an area where ships must navigate with particular caution and within which the direction of flow of traffic may be recommended.
area to be avoided - an area in which either navigation is particularly hazardous or it is exceptionally important to avoid casualties and which should be avoided by all ships, or by certain classes of ships.
